Gravitational waves revealed the size of neutron stars

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Гравитационные волны раскрыли размер нейтронных звездAstrophysicists have used all the available data about the event GW170817.

Astrophysicists were able to calculate the radius of neutron stars, of light and gravitational signals from the merger which was registered in August of 2017. The uncertainty in the estimates of this parameter significantly prevented scientists to understand the physics of the insides of these objects.

According to new data, the radius of neutron stars is approximately 11.9 miles. The results were published in joint work of employees of gravitational Observatory LIGO (USA) Virgo (Italy) in the journal Physical Review Letters.

A neutron star is one of the final stages of evolution of massive stars, they are the result of a supernova. The size of these stars is extremely small for space objects, although the mass they roughly correspond to Sun. On the internal structure of a neutron star differ from ordinary stars. Their insides are mostly characterizes the equation of state, i.e. the pressure dependence of the density.

Existing estimates of the size of neutron stars does not allow to make an unambiguous conclusion about what the equation of state characterizes their bowels. Because of this there is a great variety of models, which, in particular, includes the presence of the charm quark combinations in their cores.

In the new work, astrophysicists have used all the available data about the event GW170817, the first significant merger of two neutron stars, which was recorded as gravitational waves and electromagnetic signal in different frequency ranges. The authors analyzed the event in two ways: one is weakly dependent on the choice of a particular equation of state, and the second explicitly used the equation of state that could describe the largest known neutron star mass of 1.97 solar. In the first case the radii of the merged stars turned out was equal to 10.7 and 10.8 km with an accuracy of 20%. The second variant of the analysis of both the radius was equal to approximately 11,9 kilometers with an error of not more than 12%.

This work is unlikely to put an end to disputes about the size of neutron stars and their equation of state, at least because is based on three assumptions: both objects were typical of neutron stars, described by the same equation of state and rotated around their own axes at speeds typical of other observed double neutron stars.

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